Paperboard overlap carton



June 16, 1964 H. B. MOORS ETAL PAPERBOARD OVERLAP CARTON FIIG.I

ATTORNEY S R m m 0 TMA m u w [WK s Oll mm 2 HD l y F w w w y 7 2 I 3 7 l b .a O 5 my \I w B H; a J M United States Patent 3,137,436 YAPERBGARD OVERLAPCARTON Harold B. Moors, Richhoro, and Denis K.Hnang, Philadelphia, Pa., assignors to International Paper Company, New York, N.Y., a corporation of New York Fiied Oct. 11, 1960, Ser. No. 61,886 2 fliairns. (Cl. 2-29--48) The present invention relates to the improvement of the structural and material strength, service life, durability, and appearance of cartons and other packaging means for solids and liquids. More particularly, it relates to a process of making overlap containers having utility in the food and beverage field and the products of such process.

Broadly, overlap containers made from paperboard or the like are circular or square in their lateral cross section and, in the latter case, they are formed from a blank scored or given foldlines which define four, rectangular, larger panels and a fifth, smaller panel thereon. Each of the four larger panels adjoins at least one of the others along one of its longer sides as defined by a score or a foldline and it, when the blank is formed into the container, constitutes one of the normally vertically disposed side walls of the container. The fifth, smaller panel or, as it is commonly referred to when discussing that variety of such containers bearing the Pure-pak trademark of the Ex-Cell-O Corporation, the side seam flap extends from the fourth, larger panel along the longer side thereof not connected by a score or foldline to the third, larger panel. A score or foldline separates the fourth and fifth panels. Then, in the finished, erect container, the outside of the side seam flap and that area of the first panel adjacent to its edge are bonded together to form a seam with the aid of glue or some other adhesive. It is the lapping of the inside of such first panel over the outside of the fifth panel, usually to the locus of the foldline between the fourth and fifth panels, which gives these containers their name.

Questions of structural and material strength arise with all disposable containers made of paper board or the like, particularly when the goods sought to be packaged. are wholly or partially liquid, since any rupture or break in the structure, whether caused by having undue stresses designed into the container or placed upon the container and the blank therefor during the converting operation or normal handling, or inherent penetrability in the material leads to a loss of the goods. Hereto-fore, answers to these questions have been sought in the technique of basic stock coating. It has been suggested to precoat the stock before the containers are formed therefrom with, for example, polyethylene and it has been suggested to coat the finished containers with various agents such as waxes by dipping them into tanks thereof. However, the use of such coatings has been found not toanswer the questions fully in at least two critical areas. Areas is used advisedly here, since the problems not solved by the coating technique are precisely in the area of the overlap containers score or foldlines and in the area of its side seam.

During the manufacture of overlap container blanks and the cartons themselves, the scoring operation which defines the containers panels often abrades or ruptures either the surface of the basic paperboard or the coating on such surface if it has been precoated or both. This exposes the fibers of the stock or worse, so that a passage for moisture penetration is opened in the wall of the container, and results in a weakening of the whole structure around the score lines, particularly at the four bottom corners of the container where the strain tends to be more concentrated. This weakening is known in the trade as vertical score leaker and the problem it constitutes is one ticulars.

3,137,436 Patented June 16,1964

Ice

of those not satisfactorily solved by the methods-of coating containers heretofore known.

In addition, the construction of an overlap container is such that an outwardly directed, compression spring-like force is exerted against the inside of the first panel by the outside of the fifth panel of a four-walled container known in the'trade as the fifth panel effector side seam protrusion, a major source of structural weakness and, because of the unsightliness of the ridge or bulge it produces along the 'containers side seam, a detriment to sales appeal. Again, the. problem of side seam protrusion has not heretofore been solved by known methods of coating the containers.

Indeed, if anything, the abraded score or fold-lines and the side seam flap which give rise to the problems of vertical score leaker and fifth panel effect, respectively, tend toexacerba-te the normal difficulties of coating, as by dipping in wax, acontainer evenly and smoothly overall. Thus, for instance, it has been found that the containers geometrical configuration and the surface ten sion of the coating material normally operate to prevent the proper penetration of the coating material into the score or foldlines or the area around the containers side seam edge, i.e., the container blanks fifth panel free edge. It has-also been found that the wicking action of the exposed fibers of the free edge of the fifth panel draws the protective coating'material away in the area adjacent to such edge in the erected container leaving or making it vulnerable to moisture attack. Such attack is, of course, quite severe when the containers contents are fruit juices, chocolate milk, and syrups.- There is no reason to believe that such a wicking action is not to be found along abraded or ruptured score or foldlines and that it will not produce a similar deleterious effect at such sites.

It is an object of the present invention, then, to provide a method of improving the structural and material strength, service life, durability, and jappearance of overlap containers and a container improved in the same par- It is a further object of the present invention to provide a method of combattingand avoiding the problems vertical score leaker and fifth panel effect in overlap containers and a container having resistance to or being free of the debilitating and destructive elfects of either or both, of them.

' In accordance with the present invention, a narrow stripe of a varnish composition is applied near and parallelly to one end edge of an overlap container blank. This stripe and others like it are, preferably, applied on the inside of the blank inwardly of the similarly disposed end edge andalong one or more of the score or foldlines on the blank. and, where such score or foldlines define the five panels of the typical. four-sided overlap container on the blank therefor, the first; stripe is applied on the inside of the first panel. The other end edge of the blank which is, preferably, on the outside thereof, and of a fifth panel thereof, is then positioned to abut this first or near stripe, i.e., the stripe nearand parallel to the one end edge, between its borders and bonded to the near nets of the present invention must be moisture or, depending on the nature of the fluids to be contained, chemical resistant. It should be capable of forming a thin, smooth film and it can be chosen from among one or more of the group of polymeric materials having these characteristics which includes nitrocellulose (a pre ferred varnish component for economic reasons), vinyls, acrylates, cellulose acetate butyrate, polyolefins, phenolic resins, butadiene md styrene copolymcrs, styrene formaldehyde, and polyvinylidene chloride and its copolymers. Difierent resins and modifiers can also be incorporated into the composition. Shellacs, alkyds, dammar, or other materials can be used in the formulation to improve film adhesion, infiammability, or other characteristics of the coating.

' The various ways suitable for applying the varnish composition include printing it on the container blank with a conventional press or roller or spraying it on the blank just before the gluing operation. Whether hot melts, solutions, or emulsions of the varnish composition are employed depends largely on convenience and the manner of application. Drying rates are, for instance, a concern in printing, while viscosities are more of a concern in spraying.

For a better understanding of the invention, reference should be had to the attached drawings in which:

FIGURE 1 is a plan view of an overlap container blank having five panels; and FIGURE 2 is a sectional view of a four-sided overlap container made from the blank of FIGURE 1.

FIGURE 1 depicts a blank for a four-sided container having larger panels 1, 2, 3 and 4 which are defined or bounded, at least in part, by an end edge Ia and scores or foldlines 6, 7, 8, and 9 and having a smaller panel 5 which is defined or bounded, at least in part, by foldline 9 and the other end edge 5a. Narrow stripes 11, 12, 13 and 14 of a varnish composition applied in accordance with the method or process of the present invention overlie foldlines 6, 7, 8, and 9, respectively, on the inside 10 of the blank. Similar narrow strip 15 is positioned near and parallel to end edge Ia on the inside 10 of the blank. Inside 10 can be either the surface of the basic stock of the blank or the surface of a material with which the blank was precoated prior to the scoring operation thereon.

FIGURE 2 shows the overlap container formed from the blank of FIGURE 1 and, in particular, shows end edge 5a on the outside of panel 5 positioned to abut near strip 15 between its borders 15a and 15b to form a seam for the container. FIGURE 2 does not show the adhesive layer between end edge 5a and near stripe 15 which makes their bond permanent, but it does show a wax layer 16 which covers such bond and extends over the entire inside 10 of the container.

Tests have been conducted to measure the efficacy of the process and product of the present invention and their results are set forth in the following examples:

EXAMPLE I Four groups of overlap containers were used. Each group consisted of three containers. The first group served as a control; the second group was striped with a varnish solution of cellulose nitrate in alcohol; the third group was striped with a varnish solution of acrylate in acetone; and, the fourth group was striped with a varnish solution of polyvinyl chloride in acetone. The stripes on these containers were /z" wide and about 1 to 2 mils thick. The stripe on the inside of the first panel extended about beyond the edge of the side seam flap, i.e., the fifth panel, in the bond formed between them. Then, all the containers were machine-filled with milk, stored at 40 F., and handled periodically under identical procedures. At the end of the eighth day, of the test, the control group showed severe side seam protrusion, while the other groups showed no such ill effect.

EXAMPLE ]I Two groups of 3 containers were used. The first was used as a control and the second group was first striped with a varnish solution of a hot melt containing about polyethylene. The stripes were about 1" Wide and 3 mils thick and, in the bonds between first and fifth panels, extended about beyond the edge of the fifth panel. The containers were then machine-filled with milk and handled as in Example I. The control group showed severe signs of fifth panel effect, but the striped group had no side seam protrusion.

Other varnish compositions found suitable for use in accordance with the present invention include the following:

(I) Nitrocellulose Varnish Parts by weight Nitrocellulose, 85. type, /2 sec 10 to 25 Ethyl acetate 5 to 10 Ethanol 60 to 80 Dibutyl phthalate (plasticizer) 3 to 10 Nitrocellulose, R.S. type, V: sec 10 to 25 Ethyl acetate 10 to 15 Butyl acetate 10 to 15 Butanol 10 to 15 Ethanol 10 to 15 Dibutyl phthalate (plasticizer) 3 to 10 (II) Acrylic Varnish Methyl acrylate 10 to 25 Methyl ethyl ketone 20 to 30 Ethyl acetate 40 to 70 Dibutyl phthalate (plasticizer) 3 to 10 (III) Polyvinyl Chloride Varnish v Polyvinyl chloride 10 to 25 Methyl ethyl ketone 20 to 30 Ethyl acetate 20 to 30 Ethanol 15 to 50 Dibutyl phthalate (plasticizer) 3 to 10 What is claimed is: 1. A paperboard overlap container of liquids having first, second, third, and fourth larger panels and a fifth smaller panel defined in part by vertical end edges and foldlines, having a narrow stripe of a varnish composition near and parallelly to the first panel end edge, having the fifth panel end edge positioned to abut the near stripe between its borders, having means bonding the near stripe and the fifth panel end edge together, and having on its interior a coating to heighten the impenetrability of the paperboard to liquids.

2. A paperboard overlap container of liquids having first, second, third, and fourth larger panels and a fifth smaller panel defined in part by vertical end edges and foldlines, having narrow stripes of a varnish composition on at least one vertical foldline and near and parallelly to the first panel end edge, having the fifth panel end edge positioned to abut the near stripe between its borders. having means bonding the near stripe and the fifth panel end edge together, and having on its interior a coating to heighten the impenetrability of the paperboard to liquids.

References Cited in the file of this patent UNITED STATES PATENTS 1,897,198 Keller Feb. 14, 1933 2,200,289 Moore May 14, 1940 2,496,043 Farrell Ian. 31, 1950 2,676,745 Geisler Apr. 27, 1954 2,792,166 Brooks May 14, 1957 

2. A PAPERBOARD OVERLAP CONTAINER OF LIQUIDS HAVING FIRST, SECOND, THIRD, AND FOURTH LARGER PANELS AND A FIFTH SMALLER PANEL DEFINED IN PART BY VERTICAL END EDGES AND FOLDLINES, HAVING NARROW STRIPES OF A VARNISH COMPOSITION ON AT LEAST ONE VERTICAL FOLDLINE AND NEAR AND PARALLELLY TO THE FIRST PANEL END EDGE, HAVING THE FIFTH PANEL END EDGE POSITIONED TO ABUT THE NEAR STRIPE BETWEEN ITS BORDERS, HAVING MEANS BONDING THE NEAR STRIPE AND THE FIFTH PANEL END EDGE TOGETHER, AND HAVING ON ITS INTERIOR A COATING TO HEIGHTEN THE IMPENETRABILITY OF THE PAPERBOARD TO LIQUIDS. 